Liquid crystal displays (LCD's) are well known and typically used as the visual display screen for laptop (notebook) computers. LCD's are often (but not necessarily) backlit devices that utilize a plurality of pixels, each of which selectively allows light (either monochrome or selective colors) to pass therethrough to form images on the LCD screen. To simplify the following discussion, the present invention will be discussed in terms of outdoor viewing of laptop LCD screens; however, it will be apparent to those skilled in the art from the following discussion that the present invention may be applied to viewing other types of liquid crystal displays such as those in cell phones, camcorders, DVD players, electronic game devices, or navigation screens, and in other high brightness environments, such as in a car, plane, boat, or an office with windows.
Laptop displays, when viewed indoors, seem bright, since the light they emit is comparable or greater than typical indoor ambient light. The pupil enlarges in the low ambient indoor light levels, allowing more of the light from the laptop display to hit the retina. The enlarged pupil makes the white level of the LCD appear brighter. In addition, the reflection of indoor ambient light off the screen, often referred to as screen glare, is low compared to the brightness of the screen. This low glare allows the black level of the screen to be darker, and thus leads to a high contrast visual display.
When viewed outdoors in the daylight, however, the ambient light (even in the shade) can be brighter than a typical laptop display, making the images on the display difficult to see. The pupil shrinks in high level outdoor ambient light, preventing much of the light from the laptop display from hitting the retina, so the white level of the LCD appears darker. In addition, the glare off the screen from the bright ambient light is stronger, preventing the black levels from being dark. This combination leads to a low contrast visual display, and can be so low as to render the display unusable in that ambient light environment. Therefore, state of the art laptop screens are mostly used indoors or outside only when the ambient light levels are relatively low.
There are some prior art displays designed to be viewed outdoors, which use reflective or transflective elements that reflect ambient light through the pixels. These displays actually use the ambient light as the source of light for operation instead of or in addition to the backlight. As ambient light increases, so does the brightness of the display. However, these displays work well only at certain angles to the ambient light source, and have reduced brightness indoors. Thus, these types of displays are not typically used in laptop displays.
Therefore, it is desirable to provide a system and method to enable laptops and other devices with liquid crystal displays to be used outdoors by increasing the ratio of laptop display brightness to ambient light and reducing screen glare from bright ambient light.
It is further desirable that the system be simple, inexpensive, stylish, small and lightweight, use no power, work with any laptop, and not modify the laptop in any way.